1. Field of the Invention
This invention relates to an electronic device that is able to emit lights, and more particularly, an electronic device that is able to emit lights with high light density.
2. Description of the Prior Art
To provide light sources to a display system, such as a projector, an electronic device for emitting lights of different colors is usually used. The electronic device may control the lights of different colors by a central control circuit for saving circuit area. FIG. 1 shows an electronic device 100 according to prior art. The electronic device 100 includes a primary driver 120, switches SW1, SW2 and SW3, and light modules 110A, 110B, and 110C. The primary driver 120 has control terminals 120CA, 120CB, and 120CC for controlling the switches SW1, SW2 and SW3 respectively so as to control the light modules 110A, 110B, and 110C.
Due to different turn-on conditions of the light modules 110A, 110B, and 110C, the primary driver 120 can only turn on one light module at a time. Therefore, when turning on the light module 110A, the control terminal 120CA can turn on the switch SW1 while the control terminals 120CB and 120CC can turn off the switches SW2 and SW3. In this case, the current A1 outputted from an output terminal 120OUT of the primary driver 120 can flow only to the light module 110A and return to a ground terminal 120GND of the primary driver 120. Thus, the light modules 110B and 110C will not be turned on when the light module 110A is turned on. The similar operation principles can also be applied when turning on the light module 110B or 110C.
To control lights with different colors by the same central control circuit, the central control circuit can turn on lights of different colors sequentially. Lights of different colors can be mixed by persistence of vision to produce a desirable color.
In addition, to display high quality images, there are some more factors to be considered. For example, light density is a critical factor for a display system or a lighting system, especially for a projector operated under a rather bright environment. The image displayed by the projector can be significantly affected by ambient light if the light density of the projector is not strong enough comparing to the ambient light. Since lights of different colors are turned on and turned off in different durations by the electronic device, the light density of the lights is limited by the turn-on durations of the lights, which may decrease the image quality displayed by a display system using the electronic device. Consequently, improving the light density has become an issue to be solved.